Scheme of remote control of the slicing level of a receiver in a smart transceiver

ABSTRACT

A scheme is described of remote control of the slicing level of a receiver in a smart SFP (or SFP+, or XFP) duplex (or BiDi, or SWBiDi) transceiver in a communication system using an operating system with OAM and PP functions, an OAM, PP &amp; Payload Processor, a transceiver, a BERT, and an optical link in the field.

FIELD

Embodiments of the invention relate to a scheme of remote control of electro-optical parameters of a smart transceiver in an optical fiber communication system, and more particularly, a scheme of remote control of the slicing level or decision threshold of a receiver in the smart transceiver. The applications of embodiments of the present invention include a smart transceiver installed in communication systems without optical amplifiers as well as optically amplified systems, for example, such as long-haul transmission networks, access networks of fiber to the x (FTTx), passive optical network (PON) networks, and wireless backhauls between a base station and an antenna tower or a remote radio head (RRH), but not limited only to these systems. A smart transceiver is an intelligent transceiver that can execute Ethernet in the First Mile Operation, Administration, and Maintenance (EFM OAM) functions specified in IEEE 802.3ah, including an electrical loopback configuration. The type of the smart transceiver includes a smart small form-factor pluggable (SFP) transceiver, a smart small form-factor pluggable plus (SFP+) transceiver, and a smart 10 gigabit small form-factor pluggable (XFP) transceiver, and a Duplex smart transceiver as well as a bidirectional (BiDi) smart transceiver and a single wavelength bidirectional (SWBiDi) smart transceiver.

BACKGROUND

Setting the slicing level or decision threshold level of a receiver in a transceiver at an optimum level is very desirable since a slight offset from the optimum level will degrade significantly the bit error rate (BER) performance of a communication system. The optimum slicing level depends solely on each system in which the transceiver is operating. Here all the communication systems are grouped in three as follows: 1) communication systems without optical amplifiers, 2) optically amplified communication systems, and 3) communication systems using single-wavelength-bidirectional transceivers (SWBiDi).

For the communication systems without optical amplifiers, it is a common practice to use, on a printed circuit board (PCB) of the transceiver without any adjustment, a decision circuit such as a limiting amplifier (LA) whose slicing level is preset (default) in its IC design; the amount of offset from the optimum level is within its IC specification limits though, Considering the cost involved in optimizing the slicing level for the optimum BER performance, a further optimization of the slicing level from the default might not be attractive. As a penalty due to the non-optimum slicing level, these systems must allocate some extra margins in their system link budget where even extra 1 dB of link budget is quite often costly.

For the optically amplified systems, it is well known that the optimum slicing level is shifted from the default level toward the “0” rail due to the beat noises such as signal-amplified spontaneous emission (ASE) beat noise and ASE-ASE beat noises when the optical signal to noise ratio (OSNR) is poor. The amount of shift can be determined only after the BER in the real system is measured at various slicing levels.

For the communication systems using single-wavelength-bidirectional transceivers, it is also known that the optimum slicing level is shifted from the default level toward the “0” rail due to the interferometric beat noise (IBN) when there is reflections along the transmission path. The amount of shift can be determined only after the BER in the real system is measured at various slicing levels.

The transceiver in the optically amplified systems or in the communication systems using SWBiDi requires the adjustability of the slicing level of a receiver in the transceiver because a slight offset of the slicing level from the optimum level might be detrimental for the BER performance of the receiver, effectively making the communication systems unusable. Because a communication system consists of, at least, two transceivers and the receiver of one transceiver is receiving a signal from the transmitter of another transceiver, the controllability of the slicing level of the receiver in one transceiver by another transceiver will be a desirable feature. This is particularly true if two transceivers are physically separated far away from each other. In other words, a remote controllability of the slicing level of one transceiver by another transceiver will be very valuable, considering the facts that 1) the adjustment of its slicing level can be executed by the technician at the central office (CO) where all the necessary test equipments are accessible easily and 2) another technician does not have to be present simultaneously at the site of the transceiver which is in need of adjustment of its slicing level; this will save a lot of capital and operating expenditures (CAPEX and OPEX) by the service provider/operator.

SUMMARY

According to embodiments of the present inventions, a scheme of remote control of the slicing level or decision threshold level of a receiver in a smart transceiver may comprise a smart transceiver at a first end of the optical link, the optical link, a transceiver, an OAM, PP & Payload processor, an operating system with OAM and proprietary protocol (PP) functions, and a Bit Error Rate Test (BERT) equipment at a second end of the optical link. A PP similar to operational, administration, and maintenance protocol data unit (OAMPDU) of EFM OAM is a message protocol of changing the slicing level of a receiver in the smart transceiver.

According to embodiments of the present invention, a smart transceiver at a first end of the optical link can perform the EFM OAM in passive mode defined in IEEE802.3ah including the electrical loopback. The smart transceiver is equipped with circuitry that can adjust the slicing level of the receiver upon receiving a commanding message in a proprietary protocol from the transceiver at a second end of the optical link. The type of the smart transceiver may be SFP, or SFP+, or XFP, and Duplex, or BiDi, or SWBiDi.

According to embodiments of the present invention, an optical link may comprise an optical MUX, optical amplifier(s), optical fiber(s), and an optical demultiplexer (DEMUX).

According to embodiments of the present invention, a transceiver at a second end of the optical link can perform the EFM DAM in active mode defined in IEEE802.3ah. This transceiver can send out a commanding message of the adjustment of the slicing level of the receiver in the smart transceiver in a first end of the optical link using a PP.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements.

FIG. 1 shows a configuration for a scheme of remote control of slicing level of a receiver in a smart duplex transceiver.

FIG. 2 shows a detail functional block diagram of a smart duplex transceiver.

FIG. 3 shows a procedure for the remote control of the slicing level of a receiver in a smart duplex transceiver.

DETAILED DESCRIPTION

As shown in FIG. 1, a scheme of remote control of the slicing level of a receiver in a smart transceiver includes an operating system with OAM and PP functions 100, an OAM, PP & Payload Processor 101, a duplex transceiver 102, a BERT 103, a pair of optical fiber jumpers 104 and 105, an optical link 106, a pair of optical fiber jumpers 107 and 108, and a smart duplex transceiver 109.

As shown in FIG. 2, a smart duplex transceiver includes an optical receiver 200, electrical paths 201 and 202, an OAM, PP & Payload Processor 203, a loopback switch 204, an electrical path 205, a slicing level control circuit 206, an electrical path 207, and an optical transmitter 208.

It is assumed that the transmissions are error free in either direction, from the transceiver 102 to the smart transceiver 109, or from the smart transceiver 109 to the transceiver 102. This assumption is valid because almost all the systems in service are running in the error free region.

If, however, the transmission of a loopbacked signal starting from the transceiver 102 to the smart transceiver 109 to the transceiver 102 is not error free, first optimize the slicing level of the transceiver 102 to read the best BER. Then follow the procedures below.

Also a variable optical attenuator might be needed in between the output of the transmitter in the transceiver 102 and the optical jumper 104 if there is an allocated, big system margin, since the measured BER in the procedures below needs to be measurable with some errors in the finite measurement time period.

The following is a procedure, shown in FIG. 3, for the remote control of the slicing level of a receiver in a smart duplex transceiver 109.

Operation One

The following is the first operation 301. It is necessary, first of all, to configure the smart duplex transceiver 109 in a loopback mode. For this, a loopback OAM Protocol Data Unit (OAMPDU) generated at the operating system with OAM and PP functions 100 is sent to an OAM, PP & Payload Processor 101 where the loopback OAMPDU is encapsulated serially with the payload, if there is any. During this period, disable the output from the BERT 103. The output is sent to the transceiver 102 where the electrical signal of the loopback OAMPDU message is converted into an optical signal. Then the optical signal of the loopback message is transmitted through the optical juniper 104, the optical link 106, an optical jumper 107, and arrives at the smart diplex transceiver 109.

The optical signal arrived at the smart duplex transceiver 109 is then converted into an electrical signal at the receiver 200. The electrical signal is transmitted through the electrical path 201, and arrives at an OAM, PP & Payload Processor 203 where the loopback OAMPDU message is separated and executed. Now only the remaining payload, if there is any, passes through the OAM, PP & Payload Processor 203, an electrical path 207, and arrives at the optical transmitter 208 where the electrical payload signal is converted into an optical signal.

The optical signal of the payload from the smart transceiver 109 is transmitted through an optical jumper 108, the optical link 106, an optical jumper 105, and arrives at the transceiver 102 where the optical signal is converted into an electrical signal. The electrical signal transmits to the OAM, PP & Payload Processor 101. This completes the configuration in the loopback mode.

Operation Two

The following is the second operation 302. Enable the output from the BERT 103 and a pseudo-random bit stream is sent out at the same data rate of the communication system to the OAM, PP & Payload Processor 101, During this transmission period, do not send out any OAMPDU's and PP's in the data stream. This pseudo-random data signal will be transmitted through the path described above during the preparation of the loopback mode and then will return to the error detector of the BERT for the BER measurement. Record the Measured BER.

Operation Three

The following is the third operation 303. Disable the output of the BERT 103. Send a slicing level adjustment PP message generated at the operating system with OAM and PP functions 100 to the OAM, PP & Payload Processor 101. The output is sent to the transceiver 102 where the electrical signal of the slicing level adjustment PP message is converted into an optical signal. Then the optical signal of the slicing level adjustment PP message is transmitted through the optical jumper 104, the optical link 106, an optical jumper 107, and arrives at the smart diplex transceiver 109.

The optical signal arrived at the smart duplex transceiver 109 is then converted into an electrical signal at the receiver 200. The electrical signal is transmitted through the electrical path 201, and arrives at an OAM, PP & Payload Processor 203 where the slicing level adjustment PP message is separated. An execution message of the slicing level adjustment is sent to the slicing level control circuit 206 which adjusts the slicing level the receiver 201 accordingly.

Operation Four

The following is the fourth operation 304. Enable the output from the BERT 103 and a pseudo-random bit stream is sent out at the same data rate of the communication system to the OAM, PP & Payload Processor 101. During this transmission period, do not send out any OAMPDU's and PP's in the data stream. This pseudo-random data signal will be transmitted through the path described operation (1) above during the preparation of the loopback mode and then will return to the error detector of the BERT for the BER measurement. Record the measured BER.

Operation Five

The following is the fifth operation 305. Repeat operations (3) and (4) above at a few different slicing levels and generate a V-curve of BER vs slicing level to find the optimum slicing level.

Operation Six

The following is the sixth operation 306. Repeat operation (3) above with the optimum slicing level found in operation (5) above.

Operation Seven

The following is the seventh operation 307. Repeat operation (4) above and confirm if the measured BER is indeed what is predicted in operation (5) above.

In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. 

1-23. (canceled)
 24. A method for remotely controlling a first transceiver in an optical fiber communication system, the method comprising: configuring the first transceiver to operate in a loopback mode; iteratively measuring bit error rate (BER) on a communication link with the first transceiver, the communication link including an optical link, and sending a message to change a first decision threshold level of a receiver of the first transceiver; and determining a second decision threshold level for the receiver of the first transceiver, based on the iteratively measured BER.
 25. The method of claim 24, further comprising sending a slicing level message to the first transceiver, the slicing level message comprising information on the second decision threshold level for the receiver of the first transceiver.
 26. The method of claim 24, wherein configuring the first transceiver to operate in a loopback mode comprises: sending to the first transceiver a message comprising a loopback operational, administration, and maintenance protocol data unit (OAMPDU), the loopback OAMPDU including a loopback payload; and receiving the loopback payload from the first transceiver.
 27. The method of claim 26, further comprising disabling an output of a bit error rate test (BERT) device.
 28. The method of claim 24, wherein the first transceiver is configured to perform Ethernet in the First Mile Operation, Administration, and Maintenance (EFM OAM) functions specified in Institute of Electrical and Electronics Engineers (IEEE) 802.3 standard.
 29. The method of claim 24, wherein measuring bit error rate (BER) on a communication link with the first transceiver comprises: enabling an output of a bit error rate test (BERT) device; sending a pseudo-random (PRN) bit stream to the first transceiver; receiving the PRN bit stream from the first transceiver; and measuring BER on the communication link with the first transceiver, based on the received PRN bit stream.
 30. The method of claim 29, wherein sending a message to change a first decision threshold level of a receiver of the first transceiver comprises: disabling the output of the BERT device; and sending a slicing level message to change the first decision threshold level of the receiver of the first transceiver.
 31. The method of claim 24, wherein the first transceiver comprises a pluggable transceiver or a small form-factor pluggable transceiver.
 32. The method of claim 31, wherein the small form-factor pluggable transceiver comprises: a duplex small form-factor pluggable transceiver, a bidirectional small form-factor pluggable transceiver, a single wavelength bidirectional small form-factor pluggable transceiver, a duplex small form-factor pluggable plus transceiver, a bidirectional small form-factor pluggable plus transceiver, or a single wavelength bidirectional small form-factor pluggable plus transceiver.
 33. The method of claim 31, wherein the first transceiver is configured to support a data transmission rate of at least one gigabits per second (Gb/s).
 34. The method of claim 24, wherein the optical link comprises an optical link without optical amplifiers or an optically amplified optical link.
 35. An apparatus for remotely controlling a first transceiver in an optical fiber communication system, the apparatus comprising: one or more processors remotely located from the first transceiver; a second transceiver coupled to the one or more processors; and a bit error rate testing (BERT) device coupled to the one or more processors, wherein the one or more processors are configured to: send a configuration message, via the second transceiver, to configure the first transceiver to operate in a loopback mode; iteratively measure bit error rate (BER) on a communication link with the first transceiver, the communication link including an optical link, and send a message to change a first decision threshold level of a receiver of the first transceiver; and determine a second decision threshold level for the receiver of the first transceiver, based on the iteratively measured BER.
 36. The apparatus of claim 35, wherein the one or more processors are further configured to send a slicing level message to the first transceiver, the slicing level message comprising information on the second decision threshold level for the receiver of the first transceiver.
 37. The apparatus of claim 35, wherein the one or more processors are further configured to: send to the first transceiver a message comprising a loopback operational, administration, and maintenance protocol data unit (OAMPDU), the loopback OAMPDU including a loopback payload; and receive the loopback payload from the first transceiver.
 38. The apparatus of claim 37, wherein the one or more processors are further configured to disable an output of the BERT device.
 39. The apparatus of claim 35, wherein the first transceiver is configured to perform Ethernet in the First Mile Operation, Administration, and Maintenance (EFM OAM) functions specified in Institute of Electrical and Electronics Engineers (IEEE) 802.3 standard.
 40. The apparatus of claim 35, wherein the one or more processors are further configured to: enable an output of the BERT device; send a pseudo-random (PRN) bit stream to the first transceiver; receive the PRN bit stream from the first transceiver; and measure the BER on the communication link with the first transceiver, based on the received PRN bit stream.
 41. The apparatus of claim 40, wherein the one or more processors are further configured to: disable the output of the BERT device; and send a slicing level message to change the first decision threshold level of the receiver of the first transceiver.
 42. The apparatus of claim 35, wherein the first transceiver comprises a pluggable transceiver or a small form-factor pluggable transceiver.
 43. The apparatus of claim 42, wherein the first transceiver comprises: a duplex small form-factor pluggable transceiver, a bidirectional small form-factor pluggable transceiver, a single wavelength bidirectional small form-factor pluggable transceiver, a duplex small form-factor pluggable plus transceiver, a bidirectional small form-factor pluggable plus transceiver, or a single wavelength bidirectional small form-factor pluggable plus transceiver.
 44. The apparatus of claim 42, wherein the first transceiver is configured to support a data transmission rate of at least one gigabits per second (Gb/s).
 45. The apparatus of claim 35, wherein the optical link comprises an optical link without optical amplifiers or an optically amplified optical link. 